Zika Blood Screening Not Cost-Effective, Study Finds

Screening blood donors for Zika virus is not cost-effective in the United States or Puerto Rico, according to a study published Jan. 8 in the Annals of Internal Medicine. Despite U.S. Food and Drug Administration (FDA) requirements, analysis shows that universal screening of donated blood would only be cost-effective in the high mosquito season in Puerto Rico and never in the 50 states.

"To reduce the vulnerability of the blood supply to emerging and reemerging pathogens, public officials have responded to newly discovered transfusion-transmitted infections (TTIs) with recommendations for donor deferrals, antibody and NAT screening, and use of approved pathogen reduction technology," writes Katherine Ellingson, Ph.D., from University of Arizona, Tucson, and Matthew Kuehnert, M.D., from MTF Biologics in Edison, N.J., in an accompanying editorial.

"Successes and failures in the implementation of these strategies have led the public to expect near-zero acceptable risk for TTIs. Maintaining such low levels of risk comes at a substantial cost."

In August 2016, the FDA began requiring universal individual donor nucleic acid test (ID-NAT) screening for Zika virus in the United States and territories. In July 2018, the FDA issued revised guidance recommending universal mini-pool NAT (MP-NAT; 6 to 16 pooled sample donations) with triggers to ID-NAT during outbreaks.

The study used microsimulation to evaluate the effectiveness and cost-effectiveness of universal ID-NAT, universal MP-NAT, and alternative screening strategies, including a separate-inventory policy where donations were screened with ID-NAT or MP-NAT for components intended to be transfused to women of childbearing age and others were not screened. Other screening strategies targeted donors who resided in or had recently traveled to areas of known local transmission. For Puerto Rico, the researchers also considered seasonal strategies: either ID-NAT or MP-NAT in high mosquito season and no screening in low season and ID-NAT in high mosquito season and MP-NAT in low season.

The models aggregated costs associated with the blood centers, adverse events, and lifetime health economic consequences of adverse events due to Zika virus transfusion transmission during 1 year under each policy.

The researchers found that with no screening, an estimated 242.2 cases of transfusion transmission would have occurred during the first year of screening in Puerto Rico. Analysis found that in Puerto Rico, MP-NAT exclusively during high mosquito season was cost-effective at $81,123 per QALY.

With no intervention, an estimated 44.7 cases of transfusion transmission would have occurred during the first year of screening in the 50 states. However, no screening policy was cost-effective. The authors found that ID-NAT screening of the U.S. blood supply cost an unbelievable $341 million per quality-adjusted life-year (QALY) saved versus no screening. By comparison, MP-NAT for HIV and hepatitis B and C viruses costs about $1.3 million per QALY gained, the authors say.

"Although Zika virus has life-threatening sequelae, they were unlikely to manifest because of transfusion transmission during the period of analysis even without screening," write the authors led by W. Alton Russell, from Stanford University in California. "If the Zika virus rate among donors remained unchanged, we would expect transfusion transmission of Zika virus to result in one case of Guillain–Barre syndrome every 16 years in Puerto Rico (every 84 years in the 50 states) and 1 case of congenital Zika syndrome every 33 years in Puerto Rico (every 176 years in the 50 states) without screening."

Overall, the authors estimate that MP-NAT is cost-effective only in donor populations with rates above 1.2 in 1,000 donations and that escalation to ID-NAT is cost-effective only in populations with rates above 9.8 in 1,000 donations.

"Since the introduction of HIV antibody testing in 1985, the FDA has never discontinued screening for a TTI once required," writes Russell and colleagues. "Because the infectious donation rate drives the expected benefit and cost-effectiveness of disease marker screening, the FDA might consider identifying infectious rate thresholds for all TTIs, below which screening requirements are downgraded or eliminated. This could help ensure that blood centers allocate resources effectively, cost-efficiently, and in a prioritized manner.

Takeaway: The authors bring highlight the staggering lack of cost-effectiveness of current Zika virus screening of the U.S. blood supply.